SE-C-8202223-7 discloses a cyclone separator of the kind referred to herein, in which the filter unit comprises a truncated conical folded filter unit disposed inside a central tube connected to the central outlet, said tube entirely surrounding the filter unit. The filter unit is braced internally by means of a perforated tube of a rigid material supporting the filter unit at the inner folds, an annular gap being provided between the filter unit and the central tube. The central tube and the filter unit form a compact unit, which is resiliently suspended by means of a rubber diaphragm, so that the filter unit can be easily shaken to clean the filter surface. Dust particles adhering to the folded filter surface then easily fall out through the central tube to accumulate in the dust pocket at the bottom of the cyclone separator.
Generally, some mechanical shaking equipment of the vibrator type, an impact device or the like is used for shaking the filter unit, but the arrangement of such shaking equipment makes the Cyclone separator more complicated, and the shaking is not always effective enough to clean the filter unit.
It has been proposed in connection with dust separators having a filter unit disposed inside a central outlet between an inlet chamber for gas mixed with dust, and an outlet chamber for cleaned gas, connected to a suction source, to clean the filter unit by reversing the gas flow through the filter unit. Such a dust separator is disclosed in SE-B-8500599-9. For cleaning, the connections of the dust separator are reversed by means of two throttles so that the inlet chamber, which normally shall receive gas mixed With dust, will be connected to the suction source, and the outlet chamber instead will be the inlet chamber. Thus, the suction source will temporarily draw through the filter unit in a direction opposite to the normal direction to blow the filter unit. To effect the blowing in this manner implies complicated piping and throttle devices which are not particularly well suited for small and medium-sized cyclone separators.
As to textile barrier filters it has been proposed to utilize the pressure difference between the atmospheric pressure and the negative pressure in the filter to generate a reversed gas flow through the filter. This is described in SE-C-8007136-8. According to this publication a number of filter cartridges are each connected to an individual drum which has a side outlet to an outlet chamber for cleaned gas and opens, through an end opening, into an air reservoir at atmospheric or positive pressure. The opening is normally closed from the inside by means of a valve flap which is kept in a closed position against the pressure in the air reservoir by means of an operating device but can be swung from the closed position to another position in which the connection to the air reservoir is open, the connection of the drum to the outlet chamber for cleaned gas being closed, however. For cleaning, the valve flap is swung to said latter position to provide momentarily a reversed flow of air through the filter in order to blow the filter on equalizing the pressure difference between the air reservoir and an inlet chamber for gas mixed with dust, in which the filter cartridges are disposed. Then, the filter cartridges are cleaned one at a time, while the other cartridges are working normally filtering the supplied gas mixed with dust.